The subject matter of this disclosure relates generally to cloth seals for use with turbo-machinery such as gas turbine engines and more particularly relates to a cloth seal with reduced surface leakage therethrough.
Generally described, turbo-machinery, such as gas turbine engines and the like, includes a main gas flow path therethrough. The main gas flow path generally includes a gas intake, a compressor, a combustor, a turbine, and a gas outlet. Gas leakage, both out of the gas flow path or into the gas flow path, may be detrimental to overall engine performance and is generally otherwise undesirable. Gas path leakage may lower the efficiency of the gas turbine engine, increase fuel costs, and possibly increase emission levels.
Secondary gas flows may be used within the gas turbine engine to cool the various heated components. Specifically, cooling air extracted from the later stages of the compressor in a gas turbine engine may be used for cooling the components therein and for purging gaps and cavities between adjacent components. Cloth seals may be mounted in slots between the adjacent components so as to control the amount of the secondary flow extracted by metering its leakage into the hot gas path. Cloth seals hence are widely used to control the amount of cooling and purge air required to prevent hot gas ingestion and overheating of turbine parts such as shrouds, nozzles, and the like. Cloth seals thus may seal the gaps between adjacent turbine parts (shroud/shroud, shroud/nozzle, etc.) that are needed to accommodate typical thermal and mechanical transients during turbine engine operation. Cloth seals provide the dual advantage of effectively sealing these gaps while also providing good wear resistance due to the presence of the sacrificial cloth layers.
Reducing the leakage through the cloth seals themselves thus may reduce the amount of the secondary flow extracted from the compressor stages. Likewise, the reduced leakage through the cloth seals may result in improved overall thermal efficiency and power output from the turbine. State-of-the-art cloth seal structures rely on cloth materials to implement sealing or otherwise employ some form of protruding shim that does not adequately reduce or eliminate leakage rates any time there is a pressure drop across only the cloth portion of the seal.
There is thus a need for an improved cloth seal structure. Such an improved structure should limit leakage flow through the segment gap between adjacent seal slots. Reducing the leakage therethrough may improve the overall efficiency and power output of the gas turbine engine as a whole.